Ionizing radiation has been used to attenuate bleeding from tumors for the past three decades. See G. H. Fletcher, Textbook of Radiotherapy. Philadelphia, Lea and Febiger (1975). The primary examples of this use are in the treatment of menorrhagia from cervical carcinoma, hemoptysis from lung cancer and gastrointestinal bleeding from rectal and gastric carcinomas. The dose that is recommended to control bleeding from tumors is 400 to 500 cGy/fraction given for three consecutive days, as described by G. H. Fletcher, Textbook of Radiotherapy, Philadelphia, Lea and Febiger (1975) and by A. M. Markoe, Radiation Oncologic Emergencies, in Principles and Practice of Radiation Oncology 1267-1270 (1987). However, the efficacy of this regimen is not well documented. Moreover, the mechanism of radiation-induced control of bleeding is unknown.
Currently practiced methods of tumor specific drug delivery involve the use of antibody conjugates to liposomes and viral vectors. These methods are specific for tumor subtype or are nonspecific in localization. These limitations are significant in that, on the one hand, only certain types of tumors may be treated and, on the other hand, nonspecific localization produces undesirable collateral damage to otherwise healthy tissue.
Techniques for loading platelets have been disclosed in the art. For example, U.S. Pat. No. 5,292,524 issued to Male et al. on Mar. 8, 1994 discloses the preparation of loaded blood platelets which include a loading vehicle selected from the group consisting of liposomes and reconstituted Sendai virus envelopes. A diagnostic or therapeutic agent is encapsulated within the loading vehicle. However, there is no disclosure of a targeting technique for the loaded platelets.
U.S. Pat. No. 5,328,840 issued Jul. 12, 1994 to Coller discloses a method for preparing a targeted carrier erythrocyte by conjugating the erythrocyte with a particular polypeptide sequence. Thus, the targeting technique disclosed in Coller involves a complicated conjugation reaction.
In view of the shortcomings of the aforementioned techniques, there remains significant need in the field for advances in the tissue-selective delivery of therapeutic and imaging agents. Moreover, there remains a substantial need in the art for an improved method for the selective delivery of therapeutic or imaging agents to neoplastic tissue. Indeed, a particularly desirable method would provide for the specific delivery of a therapeutic or imaging agent to a wide variety of neoplasms while at the same time would maintain specificity for neoplastic tissue. Such a method is currently not available in the art.